import java.util.Scanner;

public class Homework6 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int c = scanner.nextInt();
        if(a==b)
        {
            System.out.println(c);
        }else if(a==c){
            System.out.println(b);
        }else{
            System.out.println(a);
        }


    }
}
